The present invention relates to a stop maintaining system of a vehicle, particularly to a stop maintaining system of a vehicle, which maintains, when the vehicle is detected to be in a stopped state, the stopped state by operating a brake force control device.
As conventional brake devices of vehicles, foot brake devices which brake vehicle wheels by applying hydraulic brake pressure to hydraulic brake mechanisms according to depression of a brake pedal, brake force control devices which include a pressurizer for increasing the hydraulic brake pressure applied to hydraulic brake mechanisms, and brake vehicle wheels by controlling the pressurizer independently from depression of a brake pedal, and electric parking brake devices which brake vehicle wheels by operating an electric brake mechanism which is driven by an electric actuator independently from depression of a brake pedal, are known.
Further, when the vehicle is detected to be in a stopped state, a burden on a driver which accompanies the depression of the brake pedal can be reduced by operating the electric parking brake device. For example, JP4674491B discloses such an art.
Generally, the electric parking brake devices change a rotational motion of the electric actuator into a linear motion by the electric brake mechanism.
Since an operational response of such an electric parking brake device is low compared with brake force control devices represented by Anti-lock Brake Systems (ABSs) and Dynamic Stability Control (DSC) systems, when the accelerator pedal is depressed by the driver, the timing for a full release of the wheel brake force by the electric parking brake device is delayed, which may degrade a starting performance of the vehicle.
Therefore, a variety of arts are proposed for maintaining a stopped state of a vehicle by a brake force control device when the vehicle is detected to be in the stopped state.
JP4788354B discloses a travel control system for a vehicle capable of autonomous travel and including a brake force control device, an abnormal state detecting module for detecting a control abnormal state of the brake force control device, and a notification device to issue a notification. When the vehicle is detected to be in a stopped state, the travel control system operates a brake force control device capable of braking vehicle wheels by controlling a pressurizer independently from depression of a brake pedal, so as to maintain the stopped state. Further, when the vehicle is detected to be in the stopped state and also the abnormal state detecting module detects the abnormal state, the travel control system operates the notification device. Thus, the driver can acknowledge the control abnormality in the brake force control device, and as a result, the vehicle is prevented from starting unintendedly to the driver after the vehicle stops.
With the art of JP4788354B, a high vehicle starting performance can be achieved at the time of depression of the accelerator pedal by the driver from the vehicle stopped state, i.e., at the time of restart.
However, with the art of JP4788354B, when the control abnormality in the brake force control device is detected, the vehicle may start contrary to the driver's intention. Therefore, the driver needs to depress the brake pedal again to operate the foot brake device, so as to maintain the stopped state of the vehicle. However, the depression of the brake pedal will lower the function of reducing the burden on the driver.
For this reason, in order to maintain the stopped state of the vehicle, it may also be considered to separately operate the electric parking brake device when the control abnormality of the brake force control device is detected.
However, if the electric parking brake device is operated, since the notification continues to be issued due to the control abnormality in the brake force control device even though the electric parking brake device can maintain the stopped state of the vehicle, the driver may be bothered.